Polybenzimidazole (PBI) resins are difficult to dissolve into a solution. Moreover, the process for dissolving PBI resins typically requires high temperatures, high pressures, and high shear rates. The solutions that can be formed require the use of exotic solvents, have low concentrations of dissolved PBI, are unstable over time without stabilizers (e.g., they gel or precipitate out). The exotic solvents include: concentrated sulfuric acid (H2SO4), formic acid, dimethyl sulfoxide (DMSO), N,N-dimethyl acetamide (DMAc), N,N-dimethyl formamide (DMF), N-methyl-2-pyrrolidone (NMP), pyridine, and a mixture of a base, a liquid sulfoxide, and water or alcohol. See U.S. Pat. Nos. Re 26,065; 3,502,606; 4,321,182; 4,785,038; 5,066,697; 5,674,614; 5,902,876; & 6,998,464, incorporated herein by reference. These unstable solutions can be stabilized. Stabilizing compounds include, for example, lithium chloride, zinc chloride, N-methyl morpholine, triethyl amine, triethanol amine, organo-lithium compounds (such as lithium stearate), and ammonium acetate. See U.S. Pat. Nos. 3,502,606; 4,321,182; & 5,066,697, incorporated herein by reference.
In the coatings industry, manufacturers prefer solutions that have high concentration, low viscosity, long shelf lives, high purity (free of contaminants like, for example, lithiums, chlorides, or the like), and are hassle-free (e.g., are provided in a ready to use form or are easily mixed, that is do not require high temperatures, pressures, and shears).
Accordingly, there is a need for a polybenzimidazole resin that can be quickly and easily (i.e., at ambient temperatures and pressures and with readily available and commonly used mixing equipment) dissolved.